EMI shielded enclosures are used when sensitive equipment or the like must be isolated from interference due to ambient electromagnetic radiation. An enclosure may also be used to confine radiation within the enclosure. A commonly used type of enclosure is a room surrounded by a layer of electrically conductive material such as metal or metal screen. Convenience and cost savings can be realized by using panels to form the walls, ceiling and floor of the enclosure. This approach permits the panels to be prefabricated as modules that can subsequently be assembled together to complete the enclosure.
A modular system includes a number of panels each having a support or frame covered with a layer of conductive material. When the panels are assembled, seams are present at the abutting panel edges. At each seam, the conductive layers of adjacent panels should be in contact so that the layers of individual panels when connected together can form an effectively continuous conductive barrier completely around the enclosure.
A typical panel used in prior modular panel systems includes a framework with edge frame members and internal frame members each rigidly attached at one end to an edge frame member and attached in a floating manner at the opposite end to an opposed edge frame member. A conductive layer overlies the framework. The fragile conductive layer is largely unsupported and is subject to damage. The addition of a rigid substrate panel between the framework and the conductive layer to reinforce and strengthen the conductive layer would result in the edge frame members being rigid and complete contact along the seams between conductive layers of abutting panels could not be consistently achieved. Bolts are used to hold the frames together at the edges of adjacent panels. Gaps in contact between the shielding layers of adjacent panels can degrade the ability of the shield to attenuate interference. If the edge frame members did flex, the rigid substrate could tear the conductive layer at the panel corners when adjacent panels were forced together.
Another difficulty can arise when the panel edges are not precisely perpendicular to the faces of the panel. It is important that the fasteners used to join the panel edges be within the shielding layer. In some cases, the conductive layers of adjacent panels may contact one another at the inner part of the seam rather than near the panel face. When this occurs, the fasteners are outside of the region of contact and can act as coupling members decreasing the desired shielding performance.